Cellular communications systems continue to grow in popularity and have become an integral part of both personal and business communications. Cellular telephones allow users to place and receive voice calls most anywhere they travel. Moreover, as cellular telephone technology has increased, so too has the functionality of cellular devices and the different types of devices available to users. For example, many cellular devices now incorporate personal digital assistant (PDA) features such as calendars, address books, task lists, etc. Moreover, such multi-function devices may also allow users to wirelessly send and receive electronic mail (email) messages and access the Internet via a cellular network and/or a wireless local area network (WLAN), for example.
Even so, as the functionality of cellular communications devices continues to increase, so too does the demand for smaller devices which are easier and more convenient for users to carry. One challenge this poses for cellular device manufacturers is designing antennas that provide desired operating characteristics within the relatively limited amount of space available for the antenna.
One approach for reducing phone size is to use flip phones having top and bottom housings connected with a hinge. The housings may be closed when the phone is not in use so that it is more compact and easier for a user to carry. One exemplary antenna system for a flip style cellular phone is described in U.S. Pat. No. 6,765,536. In particular, the antenna system includes an external antenna element carried on the top of the lower housing, and a parasitic element carried by the top housing so that when the phone is flipped open the parasitic element is in close proximity to the antenna element. A tuning circuit carried by the lower housing is electrically coupled to the parasitic element. The tuning circuit is variable to adjust the parasitic load on the antenna element to provide variable operating frequencies and bandwidths for the phone.
External cell phone antennas are advantageous in that they are spaced apart from the user's head, which makes it easier for phone manufacturers to comply with applicable specific absorption rate (SAR) requirements, for example. This is because the farther the radiating element of the cell phone antenna system is from the user, the less intense the radiation exposure to the user. Yet, many users prefer internal antennas over external antennas, as external antennas are prone to catch on objects and become damaged, for example. Yet, with the ever increasing trend towards smaller cell phone sizes, for a relatively small phone having an internal antenna, this may place the antenna in relatively close proximity to the user's ear, which may make complying with applicable SAR and/or hearing aid compatibility (HAC) requirements potentially difficult for manufacturers.
One exemplary mobile phone configuration that attempts to address radiation concerns from an internal antenna is set forth in PCT Publication No. WO/2004/021511 A2. The device includes a casing including a first in-built driven antenna element extending a length along a longest side of the casing. Either the portable communication device or the case includes at least one passive beam directive element distanced from and generally extending along at least most of the same length as the first in-built driven antenna element. Because of this, electromagnetic radiation generated by the first in-built driven antenna element is enhanced in a direction away from a side of the casing intended to be facing a user.
Despite the existence of such configurations, further improvements may be desirable in certain applications, particularly where the form factor of the device housing does not provide adequate space for such arrangements.